James R. Stoup offers these Things Every Programmer Should Know For Their First Job:

Hindsight being what it is, here are some lessons I have learned since entering the ranks of professional programming.

These tips are especially helpful for the new employee with years of experience who wonders, "Why isn't everyone listening to me?" New hires first have to prove themselves. If you reflect on your own behavior towards new hires in the past, it's obvious but you don't notice it when you're the new hire.

One tip (that I've been slow perhaps to learn) is silence never goes out of style.